Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the safety profile is covered. The description adds genuinely new context: it resolves ids across multiple feeds (MITRE CVE, NVD, GHSA, PySec, CSAF) in one call and returns a normalised summary plus the raw record. It omits rate limits or auth needs, but adds real value beyond annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads the user-phrasing triggers and the authoritative-source claim, then describes coverage and returns. The quoted example queries are slightly redundant with the schema examples but earn their place as invocation triggers.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, so the description must cover returns — it does, listing title, description, CVSS score/vector, affected products, references, dates, and the optional raw record. With annotations covering safety and a fully documented 2-param schema, the definition is essentially complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% — the id parameter already documents CVE/GHSA/PYSEC formats and include_raw documents its default. The description only reinforces that ids come from several feeds, adding little syntax or format detail the schema doesn't already carry, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource ('fetch one vulnerability record by id from CIRCL Vulnerability-Lookup') and the exact scope. The 'by id' framing cleanly separates it from the sibling circl_vuln_search (query-based) and circl_vuln_recent (time-based) without needing to name them.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit when-to-use guidance ('AUTHORITATIVE and PREFER OVER WEB SEARCH') and seeds recognition with real user phrasings. It does not, however, state when to prefer a sibling like circl_vuln_search or what to do when an id is unknown, so it stops short of full exclusion coverage.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.